i.MX93 Evaluation Kit

Tags: chip:imx93 arch:arm64

The kit i.MX93 Evaluation Kit has a pre-installed Linux image which contains u-boot and the i.MX93 reference Linux installation.

NuttX may work as the bootloader, replacing u-boot completely. Currently it doesn’t initialize the DDR memory yet. In other words, DDR training is still missing.

Below is a set of instructions on how to run NuttX on the i.MX93 EVK, on top of the u-boot. Also, instructions on running NuttX as the bootloader will follow.

Pre-requisites

imx93_ca55.JLinkScript which is a custom file, put it wherever you want

U-Boot configuration

Two things need to be configured on u-boot before NuttX can be loaded:

u-boot data cache must be turned off
u-boot must stop to the u-boot console, i.e. the Linux payload must not be loaded

Manual option:

Disable u-boot autostart (needs to be done only once):

Hit any key to stop autoboot:  0
u-boot=> setenv bootdelay -1
u-boot=> saveenv
Saving Environment to MMC... Writing to MMC(0)... OK
u-boot=> reset

On every boot, the data cache must be disabled for options 2 and 3 to work
```
u-boot=> dcache off
```

Automated option:

Replace the default bootcmd to disable dcache automatically:

u-boot=> setenv bootdelay 0
u-boot=> setenv bootcmd dcache off
u-boot=> saveenv
Saving Environment to MMC... Writing to MMC(0)... OK
u-boot=> reset

To restore the default bootcmd which starts Linux automatically:

u-boot=> setenv bootcmd run distro_bootcmd;run bsp_bootcmd
u-boot=> saveenv
Saving Environment to MMC... Writing to MMC(0)... OK
u-boot=> reset

The default bootcmd is:

u-boot=> env print bootcmd
bootcmd=run distro_bootcmd;run bsp_bootcmd

Loading and running the NuttX image

You have four options:

Load via u-boot from SD-card
Load via gdb
Load via JLink
Run from SD-card, without u-boot
Kernel build, via AHAB boot

Option 1: load via u-boot from SD-card:

Build nuttx, and move nuttx.bin to SD-card

Load from SD-card and start nuttx payload

u-boot=> dcache off; fatload mmc 1 0x80000000 nuttx.bin; go 0x80000000

Option 2: start via `gdb`:

Start JLinkGDBServer

$ JLinkGDBServer -device CORTEX-A55 -JLinkScriptFile <path_to>/imx93_ca55.JLinkScript

Start gdb

$ aarch64-none-elf-gdb

Attach and load nuttx

(gdb) target remote localhost:2331
(gdb) set mem inaccessible-by-default off
(gdb) load <path_to>/nuttx
(gdb) monitor go

Option 3: load with JLink:

Start JLink

$ JLinkExe -device CORTEX-A55 -if JTAG -jtagconf -1,-1 -speed 4000 -JLinkScriptFile <path_to>/imx93_ca55.JLinkScript

Add -AutoConnect 1 to connect automatically

$ JLinkExe -device CORTEX-A55 -if JTAG -jtagconf -1,-1 -speed 4000 -JLinkScriptFile <path_to>/imx93_ca55.JLinkScript -AutoConnect 1

Connect JLink

Connect to the debugger

Type "connect" to establish a target connection, '?' for help
J-Link>connect

You should now have a JLink prompt.

Cortex-A55 identified.
J-Link>

Load nuttx. Note that JLink expects the .elf extension, the default build output of nuttx is just “nuttx” without the extension, so it must be added to the file…
```
J-Link>LoadFile <path_to>/nuttx.elf
```

Option 4: Run from SD-card, without u-boot

Make sure CONFIG_IMX9_BOOTLOADER is set and system is configured properly for bootloader operation:
```
$ tools/configure.sh imx93-evk:bootloader
```
The build outputs a file imx9-sdimage.img. This image also contains the Ahab container. It’s required to grant Trusted Resource Domain Controller (TRDC) permissions. Flash it to an SD-card, where sdX may be sda or something else; verify the block device name properly (eg. /dev/sda, /dev/sdb etc):
```
$ sudo dd if=imx9-sdimage.img of=/dev/sdX bs=1k && sync
```
Insert the SD-card into the imx93-evk, make sure BMODE switch is [1,2,3,4] = [Off, On, Off, Off] so that it boots from the SD-card. This should boot into NuttShell in EL3 level.

Option 5: Kernel build, via AHAB boot

Follow the instructions at: https://spsdk.readthedocs.io/en/latest/examples/ahab/imx93/imx93_ahab_uboot.html to create an eMMC-bootable image (latest version of instructions tested is v2.6.1). We will be replacing the u-boot binary in step 2.3 with NuttX.
Clone both NuttX and NuttX-Apps in same level directories nuttx and apps respectively.

Configure and build NuttX:

$ cd nuttx
$ tools/configure.sh imx93-evk:knsh
$ make
$ make export

Build NuttX apps and prepare the /bin ROMFS image:

$ pushd ../apps
$ tools/mkimport.sh -z -x ../nuttx/nuttx-export-*.tar.gz
$ make import
$ tools/mkromfsimg.sh
$ mv boot_romfsimg.h ../nuttx/boards/arm64/imx9/imx93-evk/include/bin_romfsimg.h
$ popd

Re-build NuttX embedding the generated /bin ROMFS image:
```
$ make clean clean_context
$ make
```
Replace the value of the u-boot: entry in workspace/ahab_template.yaml created in step 1 above with the path to nuttx.bin.